My DS was the same, he had reflux and was just like your baby, constantly bringing up feeds. We either had full on projectile vomitting or he'd bring it up it dribs and drabs over a couple of hours.
We too tired gaviscon etc, but to be honest, nothing really worked. It was never looked into as a serious issue tbh, as he never dropped down the centiles, lord knows how he didn't, he got sick so much.
Also, are you putting the gaviscon in the bottle, or are you mixing it in a spoon and giving it to her before the bottle (assuming its still powder gaviscon!)? I thought it helped him more with the pain if we mixed it in a spoon and gave it too him before a feed.
He is six now, so this is going back a VERY long time in terms of formula milk, but we used Cow and Gate Omneo comfort, which sounds like the Aptimil you are using.
No real advice to offer re the reflux, I don't know if there is more that can be done these days, but we literally had to hold him upright after feeds, and he used to sleep in a baby chair at an angle, it was when he was laying flat that he would be the most sick.
It did get better, but it took a while to be honest, he was sick after pretty much every meal until a year.
The only problem we had with Omneo comfort was that as its a thicker milk we had the palava of experimenting with different sized teats, and it caused problems when it came to weaning as he was so full on it when he mangaged to keep it down. But then, six years ago the advice was to start solids at 16 weeks, so I don't think you would have that problem now!
I have not helped much I know, but I have been through what you are going through now and it does get better!